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LinkTest: Parallel MPI PingPong Test

The Linktest program is a parallel ping-pong test between all possible MPI connections of a machine. Output of this program is a full communication matrix which shows the bandwidth and message latency between each processor pair and a report including the minimum bandwidth. The linktest runs for n processors in n steps where in each step n/2 pairs of processors will perform the MPI pingpong test (e.g. 3 iterations, 128 kB messages). The selection of the pairs is random but after running all steps all possible pairs are covered.

Sample output of Linktest consisting of communication matrix and histogram

LinkTest is designed and optimized to run on very large numbers of MPI tasks (tested on 1.8 million tasks on JUQUEEN, Blue Gene/Q). Therefore also I/O (e.g. writing communication matrix) is implemented in parallel, using the parallel I/O library SIONlib.